Excavators and other heavy equipment have large superstructures which are rotatably mounted upon tracked undercarriages by means of turntable structures, commonly called swing hearings. Such turntables require very heavy duty bearing assemblies which are subjected to enormous strains when the equipment is in use. Thus, for example, an excavator or a long boom crane places heavy unbalanced loads upon the superstructure which must be transmitted to the undercarriage through the bearing assembly; so such bearing assemblies are particularly subject to Brinelling and other undesirable results of high localized stresses and overloads which tend to produce bearing failure.
About six years ago the idea of compliant ball races was developed for ball bearing assemblies. A compliant ball race is capable of deforming under load so as to reduce ball penetration of the raceway, lower the coefficient of friction, and reduce the tendency of the ball to Brinell the raceway.
The size and weight of devices such as excavators requires that their turntables have heavy bearing races which cannot practically be made compliant.
The heavy duty bearing assemblies required for excavators and the like constitute a particularly advantageous place to utilize crossed axis roller bearing assemblies as taught in British patent 800428. Such crossed axis roller bearing assemblies provide combined thrust and radial support. Disclosures of crossed axis roller bearings in less exacting environments are found in Hoke U.S. Pat. Nos. 2,040,741 and 2,065,311; in Dean U.S. Pat. No. 2,708,767; in Welton et al. U.S. Pat. No. 2,823,083; and in Lonngren et al U.S. Pat. No. 3,517,975.
All of the crossed axis bearing assemblies known to the present inventor either require spacing means to prevent contact between adjacent roller surfaces, or else result in marring of adjacent roller surfaces which then causes damage to the raceway surfaces.